A new surgical approach to the skull base in rats

A new procedure is described to surgically approach the rat skull base and visualize the spheno-occipital synchondrosis. This region is difficult to assess in small laboratory animals without incurring damage to midline structures. This method, however, uses a lateral approach through an anterior triangle of the neck bounded by the sternocleidomastoid, digastric (posterior belly) and omohyoid muscles. No structures are transected in this procedure, thus preserving the underlying anatomy. This oblique angle of approach allows clear visualization of the mid-basicranium while sparing retraction or surgical trauma to respiratory and digestive structures such as the larynx, trachea and esophagus.     

Retraction of the mobile descended larynx during groaning enables fallow bucks (Dama dama) to lower their formant frequencies

A permanently descended larynx is found in humans and several other species of mammals. In addition to this, the larynx of species such as fallow deer is mobile and in males it can be retracted during vocalization. The most likely explanation for the lowered retractable larynx in mammals is that it serves to exaggerate perceived body size (size exaggeration hypothesis) by decreasing the formant frequencies of calls. In this study, we quantified for the first time the elongation of the vocal tract in fallow bucks during vocalization. We also measured the effect of this vocal tract length (VTL) increase on formant frequencies (vocal tract resonances) and formant dispersion (spacing of formants). Our results show that fallow bucks increase their VTL on average by 52% during vocalization. This elongation resulted in strongly lowered formant frequencies and decreased formant dispersion. There were minimal changes to formants 1 and 2 (−0.91 and +1.9%, respectively) during vocal tract elongation, whereas formants 3, 4 and 5 decreased substantially: 18.9, 10.3 and 13.6%, respectively. Formant dispersion decreased by 12.4%. Formants are prominent in deer vocalizations and are used by males to gain information on the competitive abilities of signallers. It remains to be seen whether females also use the information that formants contain for assessing male quality before mating.     

La parole à la portée du conduit vocal de l'homme de Neandertal. Nouvelles recherches,nouvelles perspectives

Investigations about the origin of articulated language result in different interpretations dealing with the phonetic capacity of our ancestors, namely after the discovery of the Neandertals. According to anatomic arguments now called to question, principally the position of the larynx as regard to the basis of skull, some authors claimed that these fossil humans could not be endowed with speech. From a new reconstruction of the estimated position of the larynx and the vocal tract, articulatory simulations were undertaken in order to propose some potential vocalic [i a u] prototypes for Neandertals. And we can show Neandertals could pronounce vowels as differentiated as those of modern humans. To cite this article: J.-L. Heim et al., C. R. Palevol 1 (2002) 129–134.     

The coordination and interaction between respiration and deglutition in young pigs

The anatomical pathways for inspired air and ingested food cross in the pharynx of mammals, implying that breathing and swallowing must be separated either in space or in time. In this study we investigated the time relationship between swallowing and respiration in young pigs, as a model for suckling mammals. Despite the high morphological position of the larynx in young mammals, allowing liquid to pass in food channels lateral to the larynx, respiration and swallowing are not wholly independent events. Although, when suckling on a veterinary teat, the swallows occurred at various points in the respiratory cycle, there was always a period of apnea associated with the swallow. Finally, an increase in the viscosity of the milk altered this coordination, changing respiratory cycle length and also restricting the relative rate at which swallows occurred in some parts of the respiratory cycle. These results suggest that the subsequent changes in respiratory activity at weaning, associated with passage of a solid bolus over the larynx, is preceded by the ability of the animal to alter coordination between respiration and swallowing for a liquid bolus. Accepted: 29 September 1997     

The descended larynx is not uniquely human

Morphological modifications of vocal anatomy are widespread among vertebrates, and the investigation of the physiological mechanisms and adaptive functions of such variants is an important focus of research into the evolution of communication. The "descended larynx" of adult humans has traditionally been considered unique to our species, representing an adaptation for articulate speech, and debate concerning the position of the larynx in extinct hominids assumes that a lowered larynx is diagnostic of speech and language. Here, we use bioacoustic analyses of vocalizing animals, together with anatomical analyses of functional morphology, to document descended larynges in red and fallow deer. The resting position of the larynx in males of these species is similar to that in humans, and, during roaring, red-deer stags lower the larynx even further, to the sternum. These findings indicate that laryngeal descent is not uniquely human and has evolved at least twice in independent lineages. We suggest that laryngeal descent serves to elongate the vocal tract, allowing callers to exaggerate their perceived body size by decreasing vocal-tract resonant frequencies. Vocal-tract elongation is common in birds and is probably present in additional mammals. Size exaggeration provides a non-linguistic alternative hypothesis for the descent of the larynx in human evolution.     

A theoretical model of localized heat and water vapor transport in the human respiratory tract

A steady-state, one-dimensional theoretical model of human respiratory heat and water vapor transport is developed. Local mass transfer coefficients measured in a cast replica of the upper respiratory tract are incorporated into the model along with heat transfer coefficients determined from the Chilton-Colburn analogy and from data in the literature. The model agrees well with reported experimental measurements and predicts that the two most important parameters of the human air-conditioning process are: the blood temperature distribution along the airway walls, and the total cross-sectional area and perimeter of the nasal cavity. The model also shows that the larynx and pharynx can actually gain water over a respiratory cycle and are the regions of the respiratory tract most subject to drying. With slight modification, the model can be used to investigate respiratory heat and water vapor transport in high stress environments, pollutant gas uptake in the respiratory tract, and the connection between respiratory air-conditioning and the function of the mucociliary escalator.     

Morphology of the temporal skull region in tetrapods: research history,functional explanations,and a new comprehensive classification scheme

The morphology of the temporal region in the tetrapod skull traditionally has been a widely discussed feature of vertebrate anatomy. The evolution of different temporal openings in Amniota (mammals, birds, and reptiles), Lissamphibia (frogs, salamanders, and caecilians), and several extinct tetrapod groups has sparked debates on the phylogenetic, developmental, and functional background of this region in the tetrapod skull. This led most famously to the erection of different amniote taxa based on the number and position of temporal fenestrae in their skulls. However, most of these taxa are no longer recognised to represent natural groupings and the morphology of the temporal region is not necessarily an adequate trait for use in the reconstruction of amniote phylogenies. Yet, new fossil finds, most notably of parareptiles and stem-turtles, as well as modern embryological and biomechanical studies continue to provide new insights into the morphological diversity of the temporal region. Here, we introduce a novel comprehensive classification scheme for the various temporal morphotypes in all Tetrapoda that is independent of phylogeny and previous terminology and may facilitate morphological comparisons in future studies. We then review the history of research on the temporal region in the tetrapod skull. We document how, from the early 19th century with the first recognition of differences in the temporal region to the first proposals of phylogenetic relationships and their assessment over the centuries, the phylogenetic perspective on the temporal region has developed, and we highlight the controversies that still remain. We also compare the different functional and developmental drivers proposed for the observed morphological diversity and how the effects of internal and external factors on the structure of the tetrapod skull have been interpreted.     

Developmental change in the position of the fetal human larynx

The position of the mammalian larynx has been shown to be an important determinant in breathing, swallowing, and vocalizing patterns. While the growth of the adult human larynx has been studied extensively, detailed examination of fetal development has not been undertaken. Thus, crucial developmental change in the fetal period and the effects of this change on normal maturation are still unclear. This study has examined the development of the larynx and its topography during the fetal period. Thirty specimens were preserved in 10% buffered formaldehyde solution for a period of 6 weeks, after which mid-sagittal sections were performed. Fetal ages were calculated from femur diaphyseal lengths and ranged from 15 to 29 weeks. Direct measurements were taken to determine the growth and position of the larynx and trachea relative to the vertebral column and soft palate. Results show that the upper and lower levels of the larynx correspond to the basiocciput and the lower border of the third to upper border of the fourth cervical vertebrae, respectively. The epiglottic cartilage was present at 15 weeks. By 21 weeks, the epiglottis was well developed and in close palatal apposition. At 23 to 25 weeks, the epiglottis and soft palate were found to be in full contact. The acquisition of this contact may be related to fetal respiratory viability.     

Anatomical constraints generate honesty: acoustic cues to age and weight in the roars of red deer stags

Early work on loud calling in mammals emphasized the importance of dynamic characteristics such as calling rate as cues to fitness and fighting ability. In contrast, little is known of the potential for fine-scaled acoustic cues to provide receivers with direct information on fitness. Fundamental frequency has typically been considered a good potential indicator of body size in the literature, but resonance frequencies (formants), which should be constrained by the length of the vocal tract, have received less attention. We conducted a detailed acoustic analysis on an extensive database of roars from red deer stags, Cervus elaphus, in a free-ranging population to investigate which variables provided honest information on age, body weight and reproductive success. Although fundamental frequency was higher in young stags than in adults, it did not decrease with body weight within adults and source cues (i.e. those generated by the larynx) in general did not provide clear information on fitness-related characteristics. In contrast, minimum formant frequencies, reached during the part of the roar when the mobile larynx is most fully retracted towards the sternum, decreased with body weight and age and were strongly negatively correlated with our index of reproductive success. Such production-related acoustic cues to body size and fitness, rendered honest by an anatomical constraint limiting the downward movement of the larynx, provide receivers with accurate information that could be used to assess rivals and choose mates. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

The basicranium of Plio-Pleistocene hominids as an indicator of their upper respiratory systems

Our analyses of extant primates have shown that a relationship exists between the degree of flexion of the basicranium and the location of upper respiratory structures such as the larynx and pharynx (Laitman et al., 1978). Based upon these relationships, we have previously used the basicrania of late Pleistocene hominids as a guide to the reconstruction of their upper respiratory anatomy (Laitman et al., 1979). This study continues our approach by examining the basicrania of Plio-Pleistocene hominids and reconstructing their upper respiratory systems. Nine Plio-Pleistocene hominids had basicrania complete enough to be used in this study. These included the originals of Sts 5, MLD 37/38, SK 47, SK 48, SK 83, Taung, KNM-ER 406, OH 24, and a cast of OH 5. Craniometric analysis of the basicrania of these specimens showed that they had marked similarities to those of extant pongids. These basicranial similarities between Plio-Pleistocene hominids and extant apes suggest that the upper respiratory systems of these groups were also alike in appearance. As with living nonhuman primates, the early hominids probably exhibited a larynx and pharynx positioned high in the neck. This high position would have permitted an intranarial epiglottis to be present during both normal respiration and the ingestion of a liquid bolus of food. The high position of the larynx would have also greatly restricted the supralaryngeal portion of the pharynx available to modify laryngeal sounds. It is thus possible that the Plio-Pleistocene hominids exhibited modes of breathing, swallowing and vocalizing similar to those of living apes.     

Decoding the distribution of glycan receptors for human-adapted influenza A viruses in ferret respiratory tract

Ferrets are widely used as animal models for studying influenza A viral pathogenesis and transmissibility. Human-adapted influenza A viruses primarily target the upper respiratory tract in humans (infection of the lower respiratory tract is observed less frequently), while in ferrets, upon intranasal inoculation both upper and lower respiratory tract are targeted. Viral tropism is governed by distribution of complex sialylated glycan receptors in various cells/tissues of the host that are specifically recognized by influenza A virus hemagglutinin (HA), a glycoprotein on viral surface. It is generally known that upper respiratory tract of humans and ferrets predominantly express α2→6 sialylated glycan receptors. However much less is known about the fine structure of these glycan receptors and their distribution in different regions of the ferret respiratory tract. In this study, we characterize distribution of glycan receptors going beyond terminal sialic acid linkage in the cranial and caudal regions of the ferret trachea (upper respiratory tract) and lung hilar region (lower respiratory tract) by multiplexing use of various plant lectins and human-adapted HAs to stain these tissue sections. Our findings show that the sialylated glycan receptors recognized by human-adapted HAs are predominantly distributed in submucosal gland of lung hilar region as a part of O-linked glycans. Our study has implications in understanding influenza A viral pathogenesis in ferrets and also in employing ferrets as animal models for developing therapeutic strategies against influenza.     

A new fossil from the Jurassic of Patagonia reveals the early basicranial evolution and the origins of Crocodyliformes

Extant crocodylians have a limited taxonomic and ecological diversity but they belong to a lineage (Crocodylomorpha) that includes basal and rather generalized species and a highly diverse clade, Crocodyliformes. The latter was among the most successful groups of Mesozoic tetrapods, both in terms of taxonomic and ecological diversity. Crocodyliforms thrived in terrestrial, semiaquatic, and marine environments, and their fossil diversity includes carnivorous, piscivorous, insectivorous, and herbivorous species. This remarkable ecological and trophic diversity is thought only to occur in forms with a completely akinetic skull, characterized by a functionally integrated and tightly sutured braincase‐quadrate‐palate complex. However, the patterns of evolutionary change that led to the highly modified skull of crocodyliforms and that likely enabled their diversification remain poorly understood. Herein, a new basal crocodylomorph from the Late Jurassic of Patagonia is described, Almadasuchus figarii gen. et sp. nov. The new taxon is known from a well‐preserved posterior region of the skull as well as other craniomandibular and postcranial remains. Almadasuchus figarii differs from all other crocodylomorphs in the presence of six autapomorphic features, including the presence of a large lateral notch on the upper temporal bar, an otic shelf of the squamosal that is wider than long, a deep subtriangular concavity on the posterolateral surface of the squamosal, and an elongated pneumatopore on the ventral surface of the quadrate. Phylogenetic analysis focused on the origin of Crocodyliformes places Almadasuchus as the sister group of Crocodyliformes, supported by synapomorphic features of the skull (e.g. subtriangular basisphenoid, absence of basipterygoid process, absence of a sagittal ridge on the frontal, and a flat anterior skull roof with an ornamented dorsal surface). New braincase information provided by Almadasuchus and other crocodylomorphs indicates that most of the modifications on the posterior region of the skull of crocodyliforms, including the strongly sutured braincase, quadrate, and the extensive secondary palate appeared in a stepwise manner, and pre‐dated the evolutionary changes in the snout, jaws, and dentition. This indicates that the progressively increased rigidity of the skull provided the structural framework that allowed the great ecological diversification of crocodyliforms during the course of the Mesozoic. The phylogenetic pattern of character acquisition inferred for the strongly sutured (akinetic) skull and the appearance of more diverse feeding behaviours that create high mechanical loads on the skull provides another interesting parallel between the evolution of Mesozoic crocodyliforms and the evolutionary origins of mammals.     

Growth of H5N1 influenza A viruses in the upper respiratory tracts of mice

Highly pathogenic avian H5N1 influenza A viruses have spread throughout Asia, Europe, and Africa, raising serious worldwide concern about their pandemic potential. Although more than 250 people have been infected with these viruses, with a consequent high rate of mortality, the molecular mechanisms responsible for the efficient transmission of H5N1 viruses among humans remain elusive. We used a mouse model to examine the role of the amino acid at position 627 of the PB2 viral protein in efficient replication of H5N1 viruses in the mammalian respiratory tract. Viruses possessing Lys at position 627 of PB2 replicated efficiently in lungs and nasal turbinates, as well as in cells, even at the lower temperature of 33 degrees C. Those viruses possessing Glu at this position replicated less well in nasal turbinates than in lungs, and less well in cells at the lower temperature. These results suggest that Lys at PB2-627 confers to avian H5N1 viruses the advantage of efficient growth in the upper and lower respiratory tracts of mammals. Therefore, efficient viral growth in the upper respiratory tract may provide a platform for the adaptation of avian H5N1 influenza viruses to humans and for efficient person-to-person virus transmission, in the context of changes in other viral properties including specificity for human (sialic acid alpha-2,6-galactose containing) receptors.     

Combined use of a new target-centered arc system with the BRW floor stand and phantom base for a wider range of approaches and applications in stereotaxy of the head and neck

A unique target-centered arc system has been developed which combines the azimuth and declination angle approach concept of the standard BRW arc with the anteroposterior, lateral and vertical movements of the earlier Todd-Wells Guide for maximal versatility of image-guided stereotaxy. The arc system mounts on the BRW floor stand and provides completely unobstructed approaches to the upper hemisphere, base of the skull, posterior fossa or cervical region. It is ideally adapted for implant arrays and laser surgery. A new transferable phantom pointer affords target confirmation using the BRW phantom base.     

Measurement of local mass transfer coefficients in a cast model of the human upper respiratory tract

Local mass transfer coefficients measured using the naphthalene sublimation technique in an acrylic cast model of the human upper respiratory tract are reported as the Sherwood numbers for the corresponding regions. A steady air flow rate of 12 L per min was used for all measurements. Values of the Sherwood number are seen to be highest in the nasal cavity and proximal nasopharynx while a minimum value occurs just downstream from the larynx. Local values of the Nusselt number obtained in the trachea and proximal nasal cavity assuming a complete heat and mass transfer analogy agree well with in-vivo physiological measurements. The mass transfer coefficients found can be incorporated into an analytical model of respiratory heat and water vapor transfer or into a model of pollutant gas uptake in the respiratory tract.     

Effects of the laryngeal jet on nano- and microparticle transport and deposition in an approximate model of the upper tracheobronchial airways.

The extent to which laryngeal-induced flow features penetrate into the upper tracheobronchial (TB) airways and their related impact on particle transport and deposition are not well understood. The objective of this study was to evaluate the effects of including the laryngeal jet on the behavior and fate of inhaled aerosols in an approximate model of the upper TB region. The upper TB model was based on a simplified numerical reproduction of a replica cast geometry used in previous in vitro deposition experiments that extended to the sixth respiratory generation along some paths. Simulations with and without an approximate larynx were performed. Particle sizes ranging from 2.5 nm to 12 mum were considered using a well-tested Lagrangian tracking model. The model larynx was observed to significantly affect flow dynamics, including a laryngeal jet skewed toward the right wall of the trachea and a significant reverse flow in the left region of the trachea. Inclusion of the laryngeal model increased the tracheal deposition of nano- and micrometer particles by factors ranging from 2 to 10 and significantly reduced deposition in the first three bronchi of the model. Considering localized conditions, inclusion of the laryngeal approximation decreased deposition at the main carina and produced a maximum in local surface deposition density in the lobar-to-segmental bifurcations (G2-G3) for both 40-nm and 4-microm aerosols. These findings corroborate previous experiments and highlight the need to include a laryngeal representation in future computational and in vitro models of the TB region.     

Etiologic Diagnosis of Lower Respiratory Tract Infections

Decision as to the role of infection in lower respiratory tract disease requires examination by culture of specimens known to be derived from the infra-laryngeal respiratory tract. Methods that involve the upper respiratory tract in collection of specimens entail the hazard of contamination by microbiota resident in the upper respiratory tract.The extrapulmonary approaches of cutting-needle biopsy and needle aspiration of intrathoracic disease have not been impressively productive of etiologic diagnosis of infections. While open-chest surgical biopsy has been a highly effective means to diagnosis, this approach does have special requirements in facilities and technical skills.Percutaneous transtracheal aspiration of tracheo-broncho-pulmonary secretions-exudates has been productive of useful information. Because of inherent simplicity and safety, transtracheal aspiration should precede resort to more demanding, difficult, dangerous procedures.     

Ardipithecus ramidus and the evolution of language and singing: An early origin for hominin vocal capability

In this paper we analyse the possibility that the early hominin Ardipithecus ramidus had vocal capabilities far exceeding those of any extant non-human primate. We argue that erect posture combined with changes in craniofacial morphology, such as reduced facial and jaw length, not only provide evidence for increased levels of pro-sociality, but also increased vocal ability. Reduced length of the face and jaw, combined with a flexed cranial base, suggests the larynx in this species was situated deeper in the neck than in chimpanzees, a trait which may have facilitated increased vocal ability. We also provide evidence that Ar. ramidus, by virtue of its erect posture, possessed a degree of cervical lordosis significantly greater than chimpanzees. This is indicative of increased mobility of the larynx within the neck and hence increased capacity to modulate vocalisations. In the paleoanthropological literature, these changes in early hominin skull morphology have to date been analysed in terms of a shift in mating and social behaviour, with little consideration given to vocally mediated sociality. Similarly, in the literature on language evolution there is a distinct lacuna regarding links between craniofacial correlates of social and mating systems and vocal ability. These are surprising oversights given that pro-sociality and vocal capability require identical alterations to the common ancestral skull and skeletal configuration. We therefore propose a model which integrates data on whole organism morphogenesis with evidence for a potential early emergence of hominin socio-vocal adaptations. Consequently, we suggest vocal capability may have evolved much earlier than has been traditionally proposed. Instead of emerging in the Homo genus, we suggest the palaeoecological context of late Miocene and early Pliocene forests and woodlands facilitated the evolution of hominin socio-vocal capability. We also propose that paedomorphic morphogenesis of the skull via the process of self-domestication enabled increased levels of pro-social behaviour, as well as increased capacity for socially synchronous vocalisation to evolve at the base of the hominin clade.     

Opportunistic microorganisms in respiratory tract diseases in patients of the Moscow Province region

The respiratory tract microflora in patients with inflammatory processes of the upper and lower respiratory tracts in the Moscow Province region has been studied. Changes in the microflora were found to occur in patients with pyoinflammatory diseases (PID) of the upper and lower respiratory tracts have been found to occur. Gram-positive cocci, mainly staphylococci and streptococci, were shown to play the leading etiological role in the development of PID. As revealed in this study, the microorganisms detected in the inflammations of the upper and lower respiratory tracts are coagulase-negative staphylococci, mainly S. epidermidis, as well as enterococci and streptococci belonging to the group viridans.     

Skull reconstruction and ecology of <Emphasis Type="Italic">Urmiatherium polaki</Emphasis> (Bovidae,Mammalia) from the upper Miocene deposits of Maragheh,Iran

Study of a newly discovered cranial specimen of Urmiatherium polaki from Karaj Abad site in Maragheh, Iran, allows us to describe the complete skull and present a new diagnosis for this late Miocene mammal species. In the comparative study of the specimen we propose the relative position of the upper teeth as a reliable metrical method for discriminating bovids of similar size. Based on the available information, a skull reconstruction of Urmiatherium polaki is provided and its ecological profile is outlined. Both the cranial and dental features of U. polaki indicate a gregarious grazing bovid of medium size, adapted to uneven ground and exhibiting ramming as the predominant fighting behavior.